Pathfinder - Practical Guide to Eidolons

Disclaimer

I will use content from the core rules, but will intentionally omit any content not published
on the official Pathfinder SRD due to the
unmanageable volume of non-SRD content, and the wildly varying quality of non-SRD content.
If you would like me to write handbooks for specific content not published on the official
SRD, please email me and I will consider it on a case-by-case
basis. I will use the color coding scheme which has become common among Pathfinder build
handbooks. Also note that many colored items are also links to the Paizo SRD.

Red: Bad, useless options, or options which are extremely situational.

Orange: OK options, or useful options that only apply in rare circumstances

Green: Good options.

Blue: Fantastic options, often essential to the function of your character.

Temporary Note: Pathfinder Unchained and Occult Adventures were
both recently added to the SRD. I'm excited to explore them, and I am actively working
on adding their contents to my collection of handbooks. I appreciate your patience while
I make these changes.

Introduction

The Eidolon is a fantastic concept: a pet which you build from the ground up with
a pool of "evolution points". No two Eidolons look or behave the same way, and with
a bit of planning you can make an Eidolon serve nearly any purpose and fill nearly
any role in a party. Much like an Animal Companion, Eidolons typically fall into
front-line roles as strikers or defenders, but due to their intelligence and ability
to communicate, they can serve as very effective scouts.

Eidolon Abilities

HD: d10 hit points is pretty good, but it's important
to note that Eidolons don't get hit dice at the same rate as their Summoner. The hit
dice top out at 15

BAB: Full BAB is pretty great, but due to their hit
die progression Eidolons' BAB will generally keep pace with 2/3 BAB.

Good/Bad Saves: Two good saving throws is pretty good,
and the variable good saves depending on the Eidolon's base form introduces some
interesting things to think about.

Skills: By default the Eidolon gets 4 skill ranks per
hit die, but you can boost its intelligence to get extra ranks if you feel the need.
See the Eidolon Skills section below for help with skills.

Feats: There doesn't appear to be a way to retrain Eidolon
feats, so be sure to plan out your feat selections well in advance. See the Eidolon
Feats section below for help selecting feats.

Armor Bonus: Take the bonus as a natural armor bonus
every time. There is no case in which armor bonuses are better than natural armor,
and there are several things which bypass armor bonuses but not natural armor. The
bonus is pretty great, and will outpace armor and sheild bonuses very quickly.

Max. Attacks: Perhaps the biggest limitation on Eidolons'
damage ouput. Without this, Eidolons would be fairly ridiculous. Note that this is
only a limit on the number of attacks that the Eidolon can make in a turn, not on
the Eidolon's number of attack options.

Darkvision (Ex): Excellent on any and every creature in
the party.

Link (Ex): The telepathy thing is cool, but the magic
item part of the ability is far more important. Unlike Animal Companions, it is
explicitly stated that Eidolons can use magic items which work in humanoid item
slots. Give your Eidolon your belt slot for physical ability enhancements, and
maybe a ring of protection.

Ability Score Increase (Ex): A few extra ability points
probably won't make a huge difference compared to the free strength/dexterity bonus,
but you can boost your Eidolon's other abilities to get more hit points or skill ranks.

Devotion (Ex): Enchantment is a very scary spell school.

Multiattack: The rules don't specifically state that your Eidolon
can take another feat in place of multiattack, but the general rules for bonus feats
allow you to do so. Multiattack is very important, and you generally want it long
before level 10. Of course, you can plan your natural attacks so that they are all
primary attacks, at which point Multiattack is useless.

Improved Evasion (Ex): Always fantastic.

Eidolon Skills

When picking your Eidolon's skills, remember that they do not gain hit dice as
quickly as characters do, so even their best skills likely won't keep pace with a
regular party member. Eidolons get 4 skill ranks per hit die by default, but this
can be increased by improving the Eidolon's intelligence.

Free Skills

Bluff (Cha): Why? Are you planning to feint? Eidolons
don't get sneak attack, and they're not terribly charismatic.

Craft (Int): Never.

Fly (Dex): If your Eidolon can fly (and you want
it to fly), one rank here can pay off very well.

Knowledge (planes) (Int): Eidolons have 7 base
intelligence, so they're at a huge disadvantage for knowledge skills. Coupled with
their slow hit dice advancement, Eidolons will have a lot of problems contributing
meaningful amounts of knowledge.

Perception (Wis): The most rolled skill in the game,
and even with just a few ranks one more set of eyes in the party could save your
life.

Sense Motive (Wis): Worth 1 rank if you don't
need the skill ranks, but don't expect to keep up with enemy bluff modifiers.

Stealth (Dex): Crucial for scouts or ambushing.

Selected Skills

At 1st level, the summoner can choose 4 additional skills to be class skills for
his eidolon. These free skills provide a lot of versatility for your Eidolon, so be
sure to pick skills which support the role you want your Eidolon to fill.

Acrobatics (Dex): Great for Strikers to move
through combat without drawing attacks of opportunity.

Escape Artist (Dex): Very situational, and Eidolons
tend to be scary in grapples as a side-effect of their general combat scariness.

Handle Animal (Cha): Save this for the Druid.

Heal (Wis): Someone with a Wisdom bonus should take
Heal.

Intimidate (Cha): An Eidolon is not a Face.

Knowledge (Any) (Int): Eidolons have 7 base
intelligence, so they're at a huge disadvantage for knowledge skills. Coupled
with their slow hit dice advancement, Eidolons will have a lot of problems
contributing meaningful amounts of knowledge.

Linguistics (Int): An Eidolon is not a Face, and
the only thing anyone really uses Linguistics for is to learn languages.

Ride (Dex): You could, in theory, have your
Eidolon ride another creature. It could even be effective.

Sleight of Hand (Dex): Situational.

Spellcraft (Int): With 7 intelligence, this isn't
going to work well.

Survival (Wis): Situational.

Swim (Str): Just give your Eidolon a Swim speed.

Use Magic Device (Cha): Eidolons don't really
have enough Charisma to make UMD reliable, and they don't gain Hit Dice fast
enough to offset the lack of Charisma.

Eidolon Feats

Base Forms

All base forms get 5 points worth of free evolutions. The biggest differences are
their starting ability scores and their good saves.

Aquatic

Quadruped

The Quadruped is a step above other Eidolon base forms solely because it gets the
Pounce evolution. As the Eidolon grows and gains additional attacks, Pounce becomes
crucial, especially if you intend to use your Eidolon as a Striker. This limitation
is somewhat ridiculous because you can easily spend a few evolution points on any
other base form to match all of the anatomical features of the quadruped base form.
The Quadruped can also serve as a mount, which makes it very easy for the summoner
to remain adjacent to the Eidolon to share spells.

Biped

The Biped is a very versatile option. Arms and good strength make it a great
option for an area control defender, especially if you increase its size. Increasing
size to Huge and taking the Reach evolution nets you a maximum of 20 foot reach.

Serpentine

The Serpentine base form is the slowest and has the least strength of all of the
base forms. Because it has high base dexterity and starts with Reach, it can make a
good Defender, but it will have trouble dealing damage until you enhance its strength.
The Serpentine base form can be used as a mount, and because it can take Constrict,
it is an excellent grappler.

Evolutions

Evolutions are your Eidolon's heart and soul.

1-Point Evolutions

Basic Magic (Sp): All of the listed spells are bad or
can be cast by the summoner.

Bite (Ex): If your Eidolon's strength is really
high, improving the strength bonus to 1.5 could be worth an evolution point. If
your Eidolon is out of limbs to put claws on, a Bite is a decent choice.

Claws (Ex): Two primary attacks, and you can put
them on arms or legs. The gold standard of attack type evolutions.

Climb (Ex): Even more situational than Swim.

Gills (Ex): Really only necessary in aquatic
campaigns.

Hooves (Ex): Claws are considerably better, and you
don't even need Hooves for the Trample evolution.

Improved Damage (Ex): Really only good if you
have a whole bunch of one type of attack, so if you plan to use this be sure to
focus on one type of attack.

Improved Natural Armor (Ex): Not very flashy, but
additional armor never hurts.

Magic Attacks (Su): Great for bypassing DR, but
can be replaced by the Eldritch Claws feat to save evolution points, and gaining
DR/alignment allows your natural attacks to bypass DR of that alignment.

Mount (Ex): Riding your Eidolon is awesome, but
it can put you a bit too close to your enemies. Unfortunately, this is limited to
quadrupedal and serpentine forms, so you can't ride your bipedal velociraptor.

Pincers (Ex): Only take this if you plan to make
your Eidolon a Grappler. Otherwise Claws are strictly better.

Pounce (Ex): Crucial for Strikers. Take this as soon
as you have two attacks to use it with.

Pull (Ex): Add this to an attack type with reach,
can you can use your reach attacks to pull enemies into range for your other
attacks. This also allows you to significantly interfere with people trying to
move past your Eidolon, making this an excellent choice for Defenders.

Push (Ex): Why would you want to push things out of
your Eidolon's reach?

Reach (Ex): Crucial for Defenders. Not that this
only applies to one attack, not one attack type, so you may want to take this
twice if you plan to use Pull or similar abilities.

Resistance (Ex): This is a very cheap way to get
permanent energy resistance.

Scent (Ex): Scent is great for chasing down
invisible or hidden enemies.

Skilled (Ex): If you want your Eidolon to be a
Scout, throwing this in Perception or Stealth may be a good investment.

Slam (Ex): It's not clear if this gives you a
slam on both limbs, or if you only get one slam per pair of limbs. I assume that
you only get one slam based on the difference in damage between Slam and Claws,
but the difference between 1d6 and 1d8 damage is not enough to justify giving up
a second primary attack.

Sting (Ex): An extra primary attack is nice, but
the damage is relatively small, and you need to spend two evolution points to get
it. Of course, you can add poison to the Sting, which is good despite being
expensive to attain.

Swim (Ex): Very occasionally nice to have, but
not crucial unless you're in an aquatic campaign.

Tail (Ex): You really only need this for the Tail Slap
or String evolutions, which aren't great.

Tail Slap (Ex): Two evolution points for one secondary
attack is a very poor investment. Sting is considerably better.

Tentacle (Ex): Better than tail slap, but secondary
attacks are still not as good as primary attacks. The primary appeal is that you
can get this without investing in any other evolutions.

Unnatural Aura (Su): This is very cool, but not very
useful, especially for 2 evolution points.

Wing Buffet (Ex): The attacks are secondary, but
you do get two of them for one evolution point.

2-Point Evolutions

Ability Increase (Ex): Put this on Strength, and
potentially Dexterity and Constitution if you feel like you need it.

Channel Resistance (Ex): Hugely situational.

Constrict (Ex): Essential for grapplers.

Energy Attacks (Su): That's potentially a ton of
extra damage if you have enough attacks to attach it to.

Flight (Ex or Su): Flight is crucial, especially
at high levels.

Gore (Ex): A second primary attack on your head
which works alongside your bite attack. For one more point you can get an extra
set of arms and claws.

Grab (Ex): Essential for grapplers. Choose Pincers
for the extra +2 bonus unless you plan to use Swallow Whole.

Head (Ex): One head is usually plenty.

Keen Scent (Ex): This would be fantastic if it
worked above water.

Immunity (Su): Much better than resistance. At only
two points you can afford to take immunity to several elements.

Limbs (Ex): Essential to meet your maximum number
of attacks.

Minor Magic (Sp): All of the spells are fairly
weak, and will become insignificant at high levels. Vanish might be the only
option which remains useful at high levels.

Poison (Ex): The DC scales so it will stay good
at high levels. Strength damage is pretty good, but spending two points to
change it to constitution damage is extremely tempting.

Rake (Ex): Rake is normally pretty great, but
you need to be grappling to use this evolution. Quadrupeds tend to be more about
charging and pouncing than grappling, and for good reason.

Rend (Ex): Get a whole bunch of claws, get Improved
Damage for your claws, and take Rend. Rend things for huge piles of damage.

Trample (Ex): The damage isn't great, and using
Trample draws a lot of attacks of opportunity without even knocking the target
prone.

Tremorsense (Ex): Blindsense is one more point
and considerably better.

Trip (Ex): A Fantastic addition to anything with
a bite. Lead your quadruped's charges with a tripping bite attack, then mess them
up with your pile of claws.

Undead Appearance (Ex): Really only useful in an
evil party.

Weapon Training (Ex): Your Eidolon's natural
weapons will do nearly as much damage as any weapon, though their critical
hits won't be as good, and you can't enhance natural weapons. You can also use
the Eidolon's feats to get weapon proficiency if you really want it. If your
Eidolon has high enough BAB to get additional attacks, remember that you only
get iterative attacks with weapons.

Breath Weapon (Su): The damage and AOE are both
decent, but 4 points for a once per day breath weapon is just too expensive. Extra
points for additional uses is nice, a maximum of 3 uses is still not fantastic.

Fast Healing (Su): Take at least one point on every
Eidolon. As long as your Eidolon doesn't get dropped to 0 in a given fight, it's
back at full strength before the next fight. If you're a Synthesist Summoney, this
makes you nearly unkillable.

Incorporeal Form (Sp): Situational.

Large (Ex): Fantastic for a wide variety of builds.
Grapplers need it to grapple big creatures, Defenders need the reach, and every
Eidolon benefits from the huge amount of bonus strength and constitution. Upgrading
to Huge is even better in many cases.

Summoner Feats

Extra Evolution: More points means a better monster.
The "special" section of the feat text appears to be incorrect; it should say
"feat" instead of "evolution". Take this feat as often as possible.

Focused Eidolon: There are much better ways to get
bonuses on Concentration checks.

Improved Share Spell: Nice for sharing buff spells,
especially those with long durations.

Resilient Eidolon: The duration is fairly short,
but this might save your life.

Summoner's Call: A +2 ehancement bonus is nice,
but it only lasts for 10 minutes after summoning your Eidolon. Since most Summoners
will keep their Eidolon around all day long, you won't see this bonus often.